Getting Your Milkweed (and others) to Germinate in the Summer

Milkweed and Monarchs

Milkweed is an essential plant for Monarch butterflies. The leaves are the only food the Monarch caterpillars eat and the flowers are an important food source for the adults. So we should all plant some milkweed in our landscape but some people find it difficult to grow. The problem may be that milkweed seeds need cold stratification or a cold treatment to germinate. If you plant in the spring or summer the seeds will not germinate.

What is Cold Stratification?

When mother nature plants seeds in the fall, the seeds will naturally go through the process of cold stratification. It is basically exposing the seeds to cold and moist conditions that will naturally occur during the winter months. You can avoid having to do this to seeds which require it (lavender, hyssop, purple coneflower, milkweed, butterfly bush, evening primrose, scabiosa, larkspur, rudbeckia or some lupines) by planting them in the fall and allow natural cold stratification to occur over the winter. Or if you want to plant in the spring, you can mimic mother nature by following a few simple steps.

How to Cold Stratify Seeds

What you will need: Plastic bag with a zip closure, mix of one part perlite and one part vermiculite.

1. Soak the milkweed seeds in water (tap is fine) for several hours or overnight
2. After soaking, place in a plastic bag with the perlite-vermiculite mix and moisten
3. Seal bag and place in the refrigerator for 2-4 weeks
4. Check your seeds periodically to make sure they are still moist
5. After the cold treatment transfer your moist seeds to a soilless planting mix (like our Quickroot) and cover lightly with the mix.
6. Mist the soil thoroughly.
7. As the seeds are germinating keep moist but not soggy or you may get some damping off

Transplanting the Seedlings

Once your milkweed seedlings have about 2-3 sets of true leaves you can transplant them into their own pot filled with potting soil. Allow them to grow in their pot for about 6 weeks. Once they are big enough to transplant, transfer them out to the garden or landscape.

Find more information on using milkweed to grow a butterfly garden in our companion article. We also have many helpful growing supplies for sale.